Many vehicles are fitted with a hybrid drive system in which an electric motor, powered by batteries, is provided alongside an Internal Combustion Engine (ICE). In many arrangements, both the electric motor and the ICE are coupled to a drive train of the vehicle and configured to supply torque to the drive train.
In contrast to a conventional starter motor, the electric motor may be capable of delivering torque into the drive train whilst the vehicle is in motion. Hence, the hybrid electric vehicle may be capable of cranking and starting the ICE whilst the vehicle is in motion.
In some arrangements, the electric motor may be configured to provide torque to assist in driving the wheels of the vehicle, e.g. in order to allow the ICE to be smaller and/or operate closer to its optimum operating point. The electric motor may also enable the vehicle to be driven at low speeds without the use of the ICE. Additionally or alternatively, the electric motor may be configured to crank the engine, to allow the ICE to be stopped when torque is not required to drive the vehicle, for example, whilst the vehicle is coasting, braking or stopped, and restarted quickly when required.
In order to crank and restart the ICE, the electric motor may require a high voltage to be supplied from the batteries to drive the motor. If the voltage of the batteries is too low, the stop-start functionality of the vehicle may be disabled and the ICE may run constantly during operation of the hybrid vehicle.
One example approach for adjusting the output of a system battery is shown by Timmons et al. in WO2016025565A1. Therein, a controller controls switches of battery modules to bypass any identified malfunctioning battery modules. For example, the controller may transition between series, parallel, and bypassed connections so as to reduce voltage imbalance across different battery modules.
However the inventors herein have identified potential issues with such an approach. As one example, a controller may couple a set of battery modules to bypass a malfunctioning module and provide a target voltage. However, due to variations in the state of charge, state of health, and temperature of the coupled battery modules, the actual voltage provided may differ from the expected voltage, resulting in degraded hybrid vehicle performance, and increased fuel consumption due to frequent engine operation.
In one example, the above-mentioned issues may be at least partly addressed by a hybrid vehicle battery system, the battery system comprising a plurality of cells, wherein the battery system cells are electrically coupled to an electric motor of the hybrid vehicle, the electric motor being mechanically coupled to a drive system of the hybrid vehicle, wherein the hybrid vehicle has a first operating mode, in which the battery system cells provide power to the drive system, and a second operating mode, in which the battery system cells receive power from the drive system wherein the battery system further comprises one or more additional cells, selectively electrically couplable to the electric motor, wherein the battery system is configured to: determine that a state of charge of one or more cells of the battery system is below a threshold value and/or that the temperature of the battery system is below a threshold value; electrically connect the battery system cells and the additional cells together so as to increase the voltage of the battery system; and permit a stop-start operation of an internal combustion engine of the hybrid vehicle.
In one example, the battery system may be configured to determine a voltage requirement of the battery system at least partially based on a current operating mode or an anticipated operating mode of the hybrid vehicle. The battery system may be configured to adjust the configuration of the cells in order to increase or decrease the voltage of the battery system according to the voltage requirement.
The additional cells and plurality of cells may be provided in the same battery system package.
The electric motor may provide mechanical power to assist in re-starting the internal combustion engine.
The battery system may be configured to adjust the configuration of the cells at least partially based on the temperature of the battery system. Additionally or alternatively, the battery system may be configured to adjust the configuration of the cells at least partially based on the state of charge of one or more cells of the battery system
Adjusting the configuration of the cells may comprise, for example, adjusting the number of active cells within the battery system, e.g. the number of cells contributing to the voltage and/or current supplied by the battery system.
Additionally or alternatively, adjusting the configuration of the cells may comprise increasing or decreasing the number of series connections between the cells. In other words, adjusting the configuration of the cells may comprise decreasing or increasing the number of parallel connections between the cells.
The battery system may further comprise a plurality of switches configured to allow one or more of the cells to be selectively connected to the others of the cells in a plurality of configurations. For example, the plurality of switches may be configured to allow the cells to be connected in series and parallel configurations.
Additionally or alternatively, the switches may be configured to allow one or more of the cells to be selectively isolated from the others of the cells. Adjusting the configuration of the battery system may comprise isolating one or more of the cells from the others of the cells. The cells may be isolated at random.
The cells may be provided within first and second groups of cells. The configuration of the first group of cells may be adjustable and the configuration of the second group may not be adjustable.
The battery system may be configured to determine a voltage of one or more of the cells or groups of cells. The battery system may be further configured to isolate one or more of the cells or groups of cells from the others of the cells at least partially based on the voltage of the cells. Additionally or alternatively, the cells may be isolated at least partially based on the current operating mode or the anticipated operating mode of the hybrid vehicle. For example, if the current operating mode and/or the anticipated operating mode is the first operating mode, cells having a low voltage, e.g. compared to the other cells, may be isolated. If the current operating mode and/or the anticipated operating mode is the second operating mode, cells having a high voltage may be isolated.
A hybrid vehicle may comprise the above-mentioned battery system.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
To avoid unnecessary duplication of effort and repetition of text in the specification, certain features are described in relation to only one or several aspects or embodiments of the invention. However, it is to be understood that, where it is technically possible, features described in relation to any aspect or embodiment of the invention may also be used with any other aspect or embodiment of the invention.